0071643192.pdf

TOXICOLOGY

SYMPTOMS/EXAM

■ Acute toxic ingestion: Typically divided into four stages or phases (see

Table 6.22).

■ The most severe cases will develop fulminate liver failure with hepatic

encephalopathy, severe coagulopathy, renal failure, cerebral edema, and

acidosis. Liver transplantation may be indicated.

■ Repeated supra-therapeutic ingestion (chronic exposure):

■ Ingestion of >7.5 g (adults) or 150 mg/kg (child) in a 24-hour period

■ Use a 24-hour dose of 4 g (adults) and 90 mg/kg (child) if patient is

high risk for hepatotoxicity or is a febrile child <5 years.

■ Due to a subacute course, patients may present anywhere along a

spectrum: Normal LFTS to asymptomatic elevation of enzymes to

hepatic failure.

DIAGNOSIS

■ Acute ingestion (time of ingestion known) of both immediate and

extended-release formulations:

■ Obtain a 4-hour (up to 24 hours) postingestion serum aceta-

minophen level and plot the level on the Rumack-Matthew nomo-

gram (see Figure 6.2).

■ The dotted line (Rumack-Matthew line) is the original line devel-

oped from the study above which hepatotoxicity will likely occur.

■ The solid line (treatment line) is the line accepted as the standard

of care in the United States and is 25% lower as a safety margin.

■ If the patient’s serum APAP level falls above the treatment line (150

μg/mL), start treatment with N-acetylcysteine (NAC).

■ Acute ingestion (time of ingestion unknown) or repeated supra-

therapeutic ingestion.

■ An acetaminophen level CANNOT be plotted on the Rumack-

Matthew nomogram.

■ Draw an APAP level and AST/ALT at time of presentation.

■ If the APAP level is >10 mcg/mL ORthe AST/ALT are elevated, treat-

ment with NAC is recommended.

Unknown time of

acetaminophen ingestion? If

the APAP level is >10 mcg/mL

or the AST/ALT is elevated →

treat with NAC.

TABLE 6.22. Stages of Acetaminophen Poisoning Following Acute Toxic Ingestion

STAGE OFTOXICITY TIMEFROMINGESTION CLINICALFINDINGS

Stage 1(preinjury) 1/2—24 hrs Nonspecific symptoms—N/V, anorexia,

malaise

Stage 2 (injury begins) 12—72 hrs RUQ pain, rising AST/ALT, INR, bilirubin

Stage 3 (peak injury and 72—96 hrs Hepatic necrosis with resultant hepatic

sequelae) failure and sequelae; AST/ALT usually

peak at 72 hours, regardless of clinical

status

Stage 4 (Recovery) 4 days—2 wks Regeneration of liver, AST/ALT return

to baseline